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The Hawthorne Effect: a randomised, controlled trial
McCarney R, Warner J, Iliffe S, van Haselen R, Griffin M, Fisher P.. BMC medical research methodology, 2007-07-03
Topic: Risk, prevention and care in population studies
Background The 'Hawthorne Effect' may be an important factor affecting the generalisability of clinical research to routine practice, but has been little studied. Hawthorne Effects have been reported in previous clinical trials in dementia but to our knowledge, no attempt has been made to quantify them. Our aim was to compare minimal follow-up to intensive follow-up in participants in a placebo controlled trial of Ginkgo biloba for treating mild-moderate dementia. Methods Participants in a dementia trial were randomised to intensive follow-up (with comprehensive assessment visits at baseline and two, four and six months post randomisation) or minimal follow-up (with an abbreviated assessment at baseline and a full assessment at six months). Our primary outcomes were cognitive functioning (ADAS-Cog) and participant and carer-rated quality of life (QOL-AD). Results We recruited 176 participants, mainly through general practices. The main analysis was based on Intention to treat (ITT), with available data. In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 140; mean difference = -2.018; 95%CI -3.914, -0.121; p = 0.037 favouring the intensive follow-up group), and on participant-rated quality of life score (n = 142; mean difference = -1.382; 95%CI -2.642, -0.122; p = 0.032 favouring minimal follow-up group). There was no significant difference on carer quality of life. Conclusion We found that more intensive follow-up of individuals in a placebo-controlled clinical trial of Ginkgo biloba for treating mild-moderate dementia resulted in a better outcome than minimal follow-up, as measured by their cognitive functioning. Trial registration Current controlled trials: ISRCTN45577048.
Key findings
- Results We recruited 176 participants, mainly through general practices.
- In the ANCOVA model with baseline score as a co-variate, follow-up group had a significant effect on outcome at six months on the ADAS-Cog score (n = 140; mean difference = -2.018; 95%CI -3.914, -0.121; p = 0.037 favouring the intensive follow-up group), and on participant-rated quality of life score (n = 142; mean difference = -1.382; 95%CI -2.642, -0.122; p = 0.032 favouring minimal follow-up group).
- There was no significant difference on carer quality of life.
- Conclusion We found that more intensive follow-up of individuals in a placebo-controlled clinical trial of Ginkgo biloba for treating mild-moderate dementia resulted in a better outcome than minimal follow-up, as measured by their cognitive functioning.
Why it matters
In a dementia trial, participants given more intensive follow-up scored better on cognitive function and self-rated quality of life than those with minimal follow-up, but there was no significant difference in carer-rated quality of life. This shows that how often people are assessed can itself affect trial results, which matters for interpreting treatment studies.
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Study details
- Participants140
- Evidence strengthHigh
How this study scored 73/100
Published in a peer-reviewed journal, and it is a randomised controlled trial. Scored zero for effect reported because the record does not state it.
| Component | Points | Why |
|---|---|---|
| Journal tier | 7 / 10 | Tier 3 — peer-reviewed journal (BMC medical research methodology) |
| Journal's citation record | 2 / 4 | BMC Medical Research Methodology: journal h-index 221 (OpenAlex, 2026-10-29) |
| Study design | 11 / 12 | A randomised controlled trial (from PubMed type “Randomized Controlled Trial”) |
| Strength of evidence | 5 / 5 | Rated “high” in our summary |
| Peer-review validation | 10 / 10 | Peer-reviewed. Published as an article in a named peer-reviewed journal. |
| How recent | 1 / 5 | 2007 — within 20 year(s) of the newest study here |
| Sample size | 2 / 4 | 140 participants |
| Effect reported | 0 / 3 | No effect size reported — scores zero (not stated in the record — scored 0) |
| Studied in people | 3 / 3 | Studied in people (participant count stated) |
| Randomised / blinded | 2 / 2 | Randomised and blinded or placebo-controlled (as stated in the record) |
| Times cited | 7 / 7 | Cited 1,721 times (OpenAlex, 2026-10-10) |
| Citations per year | 5 / 5 | 82.0 citations a year over 21 year(s) since 2007 |
| Impact for its field and year | 4 / 6 | Cited 15.0× the average for papers of its field and year (OpenAlex FWCI) |
| Cited by studies here | 1 / 6 | Cited by 2 other studies in this library |
| Still being cited | 4 / 4 | Cited 277 times in 2024–2026 (2026 still in progress; OpenAlex) |
| Senior author's track record | 2 / 4 | Last-listed author Peter Fisher: h-index 31 (OpenAlex, whole career) |
| Institution's track record | 2 / 3 | University College London: institution h-index 2,029 (OpenAlex) |
| Multi-centre collaboration | 1 / 3 | OpenAlex lists 3 institution(s) in 1 country |
| Indexed in PubMed | 2 / 2 | Indexed in PubMed (PMID 17608932) |
| Free to read | 2 / 2 | Free to read |
| Total | 73 / 100 | — |
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Read the original
- DOI: 10.1186/1471-2288-7-30
- PubMed: 17608932
- Original source →
- Free full text: BMC Medical Research Methodology →
Full text: free to read — OpenAlex lists this copy as free to read: the link above (checked 6 Feb 1020).
Cite this study APA, Vancouver, BibTeX · download .bib or .ris
Built from the record alzhub holds for this paper, not looked up. Volume, issue and page numbers are not held in the record. Check the citation against the original before you use it.
APA 7th
McCarney, R., Warner, J., Iliffe, S., van Haselen, R., Griffin, M., & Fisher, P. (2007). The Hawthorne Effect: a randomised, controlled trial. BMC medical research methodology. https://doi.org/10.1186/1471-2288-7-30
Vancouver
McCarney R, Warner J, Iliffe S, van Haselen R, Griffin M, Fisher P. The Hawthorne Effect: a randomised, controlled trial. BMC medical research methodology. 2007. doi:10.1186/1471-2288-7-30. PMID: 17608932.
BibTeX
@article{mccarney2007-17608932,
author = {McCarney, R. and Warner, J. and Iliffe, S. and van Haselen, R. and Griffin, M. and Fisher, P.},
title = {{The Hawthorne Effect: a randomised, controlled trial}},
journal = {BMC medical research methodology},
year = {2007},
doi = {10.1186/1471-2288-7-30},
pmid = {17608932},
url = {https://doi.org/10.1186/1471-2288-7-30}
}
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